A first stage of a power supply circuit of an electrical household appliance is constructed from an AC/DC converter circuit converting an AC (alternating current) voltage to a DC (direct current) voltage. It is generally known that a phase deviation arises between the input current waveform and the voltage waveform in the inside of the converter circuit or that a phenomenon occurs that the current waveform itself does not become a sine wave. Thus, a so-called power factor decreases and hence a reactive power increases. Further, a harmonic noise is generated.
The PFC circuit is a circuit performing control such as to shape the waveform of such an AC input current into a phase and a waveform similar to those of the AC input voltage and thereby reduces the reactive power and the harmonic noise. In recent years, by the initiative of IEC (International Electro-technical Commission) which is a standardization organization, a circumstance arises that various devices are required by law to indispensably incorporate a power supply circuit of PFC control. In order that size reduction, height reduction, or the like may be achieved in a choke employed in the PFC circuit, the core employed in this is required to have a high saturation magnetic flux density, a low core loss, and an excellent direct-current superposing characteristic.
Further, in a power supply device mounted on an electric-motor driven vehicle such as a hybrid vehicle and an electric vehicle whose rapid spreading has begun in recent years, on a photovoltaic power generation apparatus, or on the like, a reactor tolerant of high currents is employed. Also in the core for such a reactor, a high saturation magnetic flux density and a low core loss are required similarly.
For the purpose of satisfying the above-mentioned requirement, a metal powder core is adopted that has a satisfactory balance between the high saturation magnetic flux density and the low core loss. The metal powder core is obtained by pressing after performing insulation treatment on the surface of magnetic powder of Fe—Si—Al family, Fe—Si family, or the like. Thus, electric resistance is improved by the insulation treatment so that eddy current loss is suppressed. As a technique relevant to this, in International Publication No. 2009/139368, for the purpose of further reduction in the core loss Pcv, a metal powder core is proposed whose main components are pulverized powder of Fe-based amorphous alloy ribbon serving as a first magnetic material and Fe-based amorphous alloy atomized powder with Cr serving as a second magnetic material.